Exsisting 2x6 attic floor joist depression.
Exsisting 2x6 attic floor joist depression.
(OP)
I have an exsisting attic with 2 2x6's sistered 16" on center over a 12' span. I have used this area for storage and overtime the sheetrock nails have popped (in the ceiling below)from the depression when holding heavy loads in the middle of the span.
When I move the weight away I can see that the nails become flush again. Currently when jumping up and down the floor has very minimal bounce and the ceiling below is and looks level and straight.
The proposed fix: sister the Joists with 1/4" x 5.25" x 11.5' flintch plate, bolted with 1/2" carrige bolts every 16" and four bolts at each end. I know the typical construction of a finch plate calls for the steel plates to be sandwiched by the 2 2x6's but they are allready in place.
Any advise on a fix to stiffen up the exsisting 2x6's would be appriciated. Maintaining the demention of the 2x6's and not removing them is the goal.
When I move the weight away I can see that the nails become flush again. Currently when jumping up and down the floor has very minimal bounce and the ceiling below is and looks level and straight.
The proposed fix: sister the Joists with 1/4" x 5.25" x 11.5' flintch plate, bolted with 1/2" carrige bolts every 16" and four bolts at each end. I know the typical construction of a finch plate calls for the steel plates to be sandwiched by the 2 2x6's but they are allready in place.
Any advise on a fix to stiffen up the exsisting 2x6's would be appriciated. Maintaining the demention of the 2x6's and not removing them is the goal.





RE: Exsisting 2x6 attic floor joist depression.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Exsisting 2x6 attic floor joist depression.
RE: Exsisting 2x6 attic floor joist depression.
The existing 2x6s joist depth is not ideal for loading. Creep can be an issue. Sistering additional wood joists or steel channels are easier solutions.
RE: Exsisting 2x6 attic floor joist depression.
Once you've decided on that, and you have a repair scheme, you might consider jacking the joists up slightly in the center, make the flitch plate or sistering repairs, then release the jack.
RE: Exsisting 2x6 attic floor joist depression.
Jacking the joists up in the middle slightly while making the retorfit was something I was considering; thanks for the suggestion, I will most likely do that now.
How would steel channels do at stiffing the joists up?
Not much experience with using them structualy.
The floor is close to the capacity of 40lbs/sf according to the floor joist span chart I have referenced the span is about 16" to long. They are doubled up so i would think that would compansate for the loading the problem is the slight deflection in the middle.
RE: Exsisting 2x6 attic floor joist depression.
RE: Exsisting 2x6 attic floor joist depression.
When I move the weight away I can see that the nails become flush again."
Sounds like the nails have pulled down from the 2X6's and need to be re-nailed, preferably screwed. I would suggest additional screws to avoid pullout.
In order to add anything and not disturb the sheetrock, any additional strengthening will have to be done from the attic space. If two 2X6 are giving you this deflection, and you have to remove any boards used to support stored materials above the 2X6's anyway, why not sister on a 2X8 instead to the (2)2X6's? The I value would be about doubled. Deflections consequently cut in half.
As it stands now, assuming HF#2 for the 2X6's, they are gooe to 40 psf live load for the 12 foot span. So, as mentioned above, deflection is the problem, plus the fastening of the sheetrock to the ceiling members.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Exsisting 2x6 attic floor joist depression.
The steel options proposed will work also but I wouldn't forget the full depth blocking at 1/3 points of the C.J. span if you go that route.